Remote plasma sources (RPS) or in-line plasma sources (IPS) have been used for abatement of perfluorocarbons (PFC's) and global warming gases (GWG's). For example, the RPS or IPS may be installed in a foreline of a vacuum system of a substrate processing system between a high vacuum pump, such as a turbo pump, and a backing pump, such as a dry vacuum pump. In some plasma abatement systems, a reagent delivery system (RDS), such as a water delivery system (WDS), delivers water vapor to the foreline as a reagent gas for the PFC abatement process.
The inventor has observed that the evaporation of the water in the WDS causes cooling, and as the vapor flow rate is increased, the surface of liquid water in the WDS may freeze and choke off the flow of water vapor. In addition, the inventor has observed that the scaling up of the WDS to support multiple process chambers includes increasing of the water tank size which causes the freezing problem to become more acute. Specifically, since it is more difficult to transfer heat to the inner section of the larger tank, the surface of the water in the tank is more prone to freezing.
Therefore, the inventors have provided embodiments of an improved reagent delivery system including a heat exchanger to prevent surface freezing of the reagent and allow higher reagent vapor evaporation flow rate.